Heretofore, a superconducting lead wire prepared by embedding a superconducting filament such as a Nb--Ti alloy bar into copper matrix has been employed as a conductor for superconducting magnet.
Such superconducting lead wire as described above is manufactured in accordance with, for example, the following manner. First, a Nb--Ti alloy bar is inserted into a copper tube to produce a composite billet, a Cu/Nb--Ti composite bar is produced in accordance with hydrostatic pressure extrusion, and then diameter of the resulting composite bar is reduced by wire drawing process. Furthermore, a plurality of Cu/Nb--Ti composite bars are made up into a bundle, and a copper or a copper alloy tube is again filled with the resulting bundle to prepare a composite billet, and thereafter a superconducting single wire is produced in accordance with the above-mentioned process. Then, a required number of the superconducting single wires are stranded with each other thereby to manufacture a superconducting lead wire.
A superconductor is prepared by including a pure aluminum which is covered with a Cu--2Ni alloy which is used as a cladding material disposed under a superconducting strand composed of a plurality of the Cu/Nb--Ti superconducting single wires, and coating these materials with copper used for stabilization. The superconductor thus constituted exhibits excellent mechanical strength.
Moreover, another conventional aluminum stabilized superconductor has been disclosed in Japanese Patent Application Laid-Open No. 5-74235. This aluminum stabilized superconductor has such structure wherein a superconducting strand composed of a plurality of Cu/Nb--Ti superconducting single wires is covered with an aluminum alloy for stabilization which is prepared by adding a predetermined amount of Cu and Si to pure aluminum, respectively, for increasing mechanical strength of the superconductor.
However, according to the former conventional superconductor, it is difficult to achieve light weight and downsizing thereof, because the stabilizing material (stabilizer) is made from copper and there is use of a cladding material.
On the other hand, according to the latter conventional superconductor, although light weight and downsizing thereof can be achieved, it is insufficient in mechanical strength as well as in thermal and electrical stability, because an adding amount of Cu and Si is not suitable, respectively.